biological weaponalso called germ weaponany of a number of disease-producing agents—such as bacteria, viruses, rickettsiae, fungi, toxins, or other biological agents—that may be utilized as weapons against humans, animals, or plants.

The direct use of infectious agents and poisons against enemy personnel is an ancient practice in warfare. Indeed, in many conflicts diseases have been responsible for more deaths than all the employed combat arms combined, even when they have not consciously been used as weapons.

Biological weapons, like chemical weapons, radiological weapons, and nuclear weapons, are commonly referred to as weapons of mass destruction, although the term is not truly appropriate in the case of biological armaments. Lethal biological weapons may be capable of causing mass deaths, but they are incapable of mass destruction of infrastructure, buildings, or equipment. Nevertheless, because of the indiscriminate nature of these weapons, as well as the potential for starting widespread pandemics, the difficulty of controlling disease effects, and the simple fear that they inspire, most countries have agreed to ban the entire class. A total of 171 177 countries have signed, and of that number 155 164 have ratified, the Biological Weapons Convention (BWC), which was opened for signature in 1972. Under the terms of the BWC, member states are prohibited from using biological weapons in warfare and from developing, testing, producing, stockpiling, or deploying them. Nevertheless, a number of states have continued to pursue biological warfare capabilities, seeking a cheaper but still deadly strategic weapon rather than following the more difficult and expensive path to nuclear weapons. In addition, the threat that some deranged individual or terrorist organization will manufacture or steal biological weapons is a growing security concern.

Biological warfare agents

Biological warfare agents differ greatly in the type of organism or toxin used in a weapons system, lethality, length of incubation, infectiousness, stability, and ability to be treated with current vaccines and medicines. There are five different categories of biological agents that could be weaponized and used in warfare or terrorism. These include:

Bacteria—single-cell organisms that cause diseases such as anthrax, brucellosis, tularemia, and plague.Rickettsiae—microorganisms that resemble bacteria but differ in that they are intracellular parasites that reproduce inside cells; typhus and Q fever are examples of diseases caused by rickettsia organisms.Viruses—intracellular parasites, about 1100 the size of bacteria, that can be weaponized to cause diseases such as Venezuelan equine encephalitis.Fungi—pathogens that can be weaponized for use against crops to cause such diseases as rice blast, cereal rust, wheat smut, and potato blight.Toxins—poisons that can be weaponized after extraction from snakes, insects, spiders, marine organisms, plants, bacteria, fungi, and animals; an example of a toxin is ricin, which is derived from the seed of the castor bean.

Some of these biological agents have properties that would make them more likely candidates for weaponization owing to their lethality, ability to incapacitate, contagiousness or noncontagiousness, and hardiness and stability, and other characteristics.

Among the agents deemed likely candidates for biological weapons use are the toxins ricin, staphylococcal enterotoxin B (SEB), botulinum toxin, and T-2 mycotoxin and the infectious agents responsible for anthrax, brucellosis, cholera, pneumonic plague, tularemia, Q fever, smallpox, glanders, Venezuelan equine encephalitis, and viral hemorrhagic fever. In addition, various states at various times have looked into weaponizing dozens of other biological agents.

Defense against biological weapons

Military defense

Most weaponized lethal biological agents are intended to be delivered as aerosols, which would cause infections when breathed by the targeted personnel. For this reason, the most effective defense against biological weapons is a good protective mask equipped with filters capable of blocking bacteria, viruses, and spores larger than one micron (one micrometre; one-millionth of a metre) in cross section from entry into the wearer’s nasal passages and lungs. Protective overgarments, including boots and gloves, are useful for preventing biological agents from contacting open wounds or breaks in the skin. Also, decontaminants can neutralize biological agents in infected areas after a biological attack.

Developing and fielding effective biological weapon sensors that can trigger an alarm would allow personnel to don masks before exposure, get into protective overgarments, and go inside, preferably into toxic-free collective protection shelters. Medical teams could then immediately go into action to check and treat those who may have been exposed.

Biological warfare attacks can be made less effective, or ineffective, if the targeted persons have been vaccinated against the specific disease-causing agent used in an attack.

Civil defense

Civil defense against biological weapons has greatly improved since the Sept. September 11, 2001, attacks in the United States, but progress does not necessarily equal success. A successful civil defense against major biological attacks requires that significant progress be made in sensors, warning systems, vaccines, medicines, training of responders, and public education, as well as in planning of emergency procedures. These aspects of civil defense are described briefly in this section, using as examples certain practices put into effect in the United States since September 11.

The foundation of any civil defense against a biological weapons attack is the medical system that has already been set up to deal with naturally occurring diseases. Special vaccines have been created, tested, and approved to deal with the two most lethal biological agents that can also be most easily weaponized: anthrax and smallpox. For example, the U.S. government has enough smallpox vaccine to vaccinate the entire American population and enough anthrax vaccine to inoculate at least every member of the U.S. military.

Effective vaccines for plague and cholera now exist and have been approved for use, but only small quantities have been produced, far short of what might be needed if large numbers of people were to be infected. Furthermore, in the United States a number of vaccines are still in the Investigational New Drug (IND) category and await further trials before the Federal Drug Administration (FDA) can validate their effectiveness and safety. Included among these are vaccines for Q fever, tularemia, Venezuelan equine encephalitis, viral hemorrhagic fever, and botulism.

At present no effective vaccines exist for preventing infections from glanders, brucellosis, staphylococcal enterotoxin B, ricin, or T-2 mycotoxins—all biological agents that some countries have researched for military use or have weaponized in the past. However, in some cases where vaccines are not yet available, medicines have been developed that help the sick to recover.

Long-term medical research is being conducted to investigate the possibility of developing vaccines and supplements that, when administered, might raise the effectiveness of the recipient’s immune system to protect against the whole spectrum of probable biological weapon agents.

One U.S. civil defense program that might make a difference in a biological emergency is the Strategic National Stockpile program, which has created 50-ton “push packages” of vaccines, medicines, decontamination agents, and emergency medical equipment, which are stored in a dozen locations across the country in preparation for emergencies. Furthermore, every U.S. state has bioterrorism response plans in place, including plans or guidelines for mass vaccinations, triage, and quarantines. The U.S. Centers for Disease Control and Prevention (CDC) has also drafted model legislation on emergency health powers for states to adopt in order to deal with such crises.

A new emergency response system was created in the United States following the September 11 attacks. The National Guard also increased the number of its Weapons of Mass Destruction Civil Support Teams, which respond to chemical, biological, radiological, or nuclear weapons attacks—augmenting the police, fire, and medical first responders in the local area of any attacks. In addition, the Department of Homeland Security, working with the Department of Health and Human Services, invested heavily in passive defenses against biological attacks, focusing on such programs as Project BioShield and the Laboratory Response Network. The CDC also embarked on a training program on bioterrorism for thousands of medical lab technicians, and the National Institutes of Health funded new biocontainment research laboratories to further research in vaccines, medicines, and bioforensics.

Sensors to detect the presence of biological agents in the air, in water, or on surfaces are still relatively ineffective, but the aim of research is to create a “detect-to-warn” system that would provide enough time for potential victims to don masks, cover up, and take shelter before they were infected. The current “detect-to-treat” capability is unsatisfactory, since responders would be treating many persons already infected. Most current biological detectors are point detectors, which are not capable of giving advance warning after scanning an airborne cloud of particles to discern if those particles contain biological agents of a specific type.

Biological weapons in history

Pre-20th-century use of biological weapons

One of the first recorded uses of biological warfare occurred in 1347, when Mongol forces are reported to have catapulted plague-infested bodies over the walls into the Black Sea port of Caffa (now Feodosiya, Ukr.Ukraine), at that time a Genoese trade centre in the Crimean Peninsula. Some historians believe that ships from the besieged city returned to Italy with plague, starting the Black Death pandemic that swept through Europe over the next four years and killed some 25 million people (about one-third of the population).

In 1710 a Russian army fighting Swedish forces barricaded in Reval (now Tallinn, Est.Estonia) also hurled plague-infested corpses over the city’s walls. In 1763 British troops besieged at Fort Pitt (now Pittsburgh) during Pontiac’s Rebellion passed blankets infected with smallpox virus to the Indians, causing a devastating epidemic among their ranks.

Biological weapons in the world warsWorld Wars

During World War I (1914–18), Germany initiated a clandestine program to infect horses and cattle owned by Allied armies on both the Western and Eastern fronts. The infectious agent for glanders was reported to have been used. For example, German agents infiltrated into the United States and surreptitiously infected animals prior to their shipment across the Atlantic in support of Allied forces. In addition, there reportedly was a German attempt in 1915 to spread plague in St. Petersburg in order to weaken Russian resistance.

The horrors of World War I caused most countries to sign the 1925 Geneva Protocol banning the use of biological and chemical weapons in war. Nevertheless, Japan, one of the signatory parties to the protocol, engaged in a massive and clandestine research, development, production, and testing program in biological warfare, and it violated the treaty’s ban when it used biological weapons against Allied forces in China between 1937 and 1945. The Japanese not only used biological weapons in China, but they also experimented on and killed more than 3,000 human subjects (including Allied prisoners of war) in tests of biological warfare agents and various biological weapons delivery mechanisms. The Japanese experimented with the infectious agents for bubonic plague, anthrax, typhus, smallpox, yellow fever, tularemia, hepatitis, cholera, gas gangrene, and glanders, among others.

Although there is no documented evidence of any other use of biological weapons in World War II, both sides had active research and development (R&D) programs. The Japanese use of biological warfare agents against the Chinese led to an American decision to undertake biological warfare research in order to understand better how to defend against the threat and provide, if necessary, a retaliatory capability. The United Kingdom, Germany, and the Soviet Union had similar R&D programs during World War II, but only Japan has been proved to have used such weapons in the war.

Biological weapons in the Cold War

In the Cold War era, which followed World War II, both the Soviet Union and the United States, as well as their respective allies, embarked on large-scale biological warfare R&D and weapons production programs. These programs were required by law to be halted and dismantled upon the signing of the Biological Weapons Convention (BWC) in 1972 and the entry into force of that treaty in 1975. In the case of the United States and its allies, compliance with the terms of the treaty appears to have been complete. Such was not the case with the Soviet Union, which conducted an aggressive clandestine biological warfare program even though it had signed and ratified the treaty. The lack of a verification regime to check members’ compliance with the BWC made it easier for the Soviets to flout the treaty without being detected.

After the demise of the Soviet Union in 1991 and its subsequent division into 15 independent states, Russian Pres. Boris Yeltsin confirmed that the Soviet Union had violated the BWC, and he pledged to terminate what remained of the old Soviet biological weapons program. (See also yellow rain.) However, another problem remained—that of the potential transfer of information, technical assistance, production equipment, materials, and even finished biological weapons to states and groups outside the borders of the former Soviet Union. The United States and the former Soviet republics pledged to work together to contain the spread of biological warfare capabilities. With financing from the U.S. Cooperative Threat Reduction Program and other sources, help in obtaining civilian jobs in other fields was also made available for some of the estimated 60,000 scientists and technicians who worked in the Soviet biological warfare programs.

Biological weapons proliferation

Of the more than 190 members of the United Nations, only a dozen or so are strongly suspected of having ongoing biological weapons programs. However, such programs can be easily hidden and disguised as vaccine plants and benign pharmaceutical production centres. Biological weapons are not as expensive to manufacture as nuclear weapons, yet a lethal biological weapon might nonetheless be the strategic weapon that would win a war. This prospect of military advantage might tempt some regimes to acquire the weapons, though perhaps clandestinely.

Since the Biological Weapons Convention (BWC) has no existing verification or inspection procedures to verify compliance by its signatories, cheating on the treaty might be done with no outside proof to the contrary. It is entirely possible that even a small and relatively poor state might successfully embark on a biological warfare program with a small capital investment and a few dozen biologists, all of which could be secretly housed within a few buildings. In fact, a biological weapons program might also be within the technical and financial reach of a terrorist organization (see below). In summary, the degree of biological weapons proliferation is highly uncertain, difficult to detect, and difficult to quantify.

Biological terrorism

Biological weapons have been used in a few instances in the past by terrorist organizations. In the 1980s, followers of the exiled Indian self-proclaimed guru Bhagwan Shree Rajneesh settled on a ranch in Wasco county, Oregon. The “Rajneeshies” took political control of the nearby town of Antelope, changing its name to Rajneesh, and in 1984 they attempted to extend their political control throughout the county by suppressing voter turnout in the more populous town of The Dalles. Leading up to the countywide elections, cult members experimented with contaminating groceries, restaurants, and the water supply in The Dalles with Salmonella bacteria. Their efforts made at least 751 people ill. The plot was not discovered until the year after the attack, when one of the participants confessed.

In the period from April 1990 to July 1995, the AUM Shinrikyo sect used both biological and chemical weapons on targets in Japan. The members’ biological attacks were largely unsuccessful because they never mastered the science and technology of biological warfare; nevertheless, they attempted four attacks using anthrax and six using botulinum toxin on various targets, including a U.S. naval base at Yokosuka.

Al-Qaeda operatives have shown an interest in developing and using biological weapons, and they operated an anthrax laboratory in Afghanistan prior to its being overrun by U.S. and Afghan Northern Alliance forces in 2001–02. In 2001 anthrax-laden letters were sent to many politicians and other prominent individuals in the United States. The letters killed 5 people and sent 22 to the hospital while forcing the evacuation of congressional office buildings, the offices of the governor of New York, several television network headquarters, and a tabloid newspaper office. This event caused many billions of dollars in cleanup, decontamination, and investigation costs. In early 2010, more than eight years after the mailings, the Federal Bureau of Investigation finally closed its investigation, having concluded that the letters had been mailed by a microbiologist who had worked in the U.S. Army’s biological defense effort for years and who had committed suicide in 2008 after being named a suspect in the investigation.

Information on the manufacture of biological and chemical weapons has been disseminated widely on the Internet, and basic scientific information is also within the reach of many researchers at biological laboratories around the world. Unfortunately, it thus seems likely that poisons and disease agents will be used as terrorist weapons in the future.